Synthetic lubricant



Patented Jan. 7, 1241 PATENTS other.

SYNTHETIC LUBRICANT William B. Plummer, Chicago, Ill., assignor toStandard Oil Company, Chicago, 111., a corporation of Indiana NoDrawing. Application June 29, 1939, Serial No. 281,920

" 7 Claims. (01. 252-45) This invention relates to improvements insynthetic lubricating oils and particularly to synthetic lubricatingoils for use in internal combustion engines.

6 With recnt advances in petroleum research, there have been developed anumber of synthetic lubricating oils prepared by polymerization,hydrogenation and the like. Thus synthetic lubricating oils have beenprepared by the condensa- 10 tion of diphenyl-in the presence ofaluminum chloride as described in U. S. Patent 2,030,832; by thepolymerization of isobutylene in the presence of boron fluoride asdescribed in ,the co-pending application of E. R. Barnard, Serial No.237,145; by the polymerization of cracked paraffin wax in the presenceof aluminum chloride as taught by I U. S. Patents 1,955,260, 2,091,398and others.

While synthetic lubricating oils have many highly desirable propertiessuch as for example 20 lowpour-xpoints, low Conradson carbon, oxidationstability, high viscosity indices, etc. they do not in general possessgood lubricating properties. Where synthetic oils have been employed ininternal combustion engines, difliculty has been encountered with scoredand scuffed pistons and cylinder walls and feathering of piston rings.This deficiency in lubricating quality has greatly hindered theextensive use of synthetic lubricating oils and although the lubricityof these oils 30 -may be improved by the addition of certain additionagents, this increases the cost. of the already relatively expensivelubricating oils. Therefore, this remedy is an undesirable one from aneconomic viewpoint. 35 It is, therefore, the primary object of thepresent invention to provide a synthetic lubricating oil whichpossessesgood lubricating qualities. It is a further object of thepresent invention to provide a synthetic lubricating oil adapted for use40 in internal combustion engines which will not score and scuff pistonsand cylinder walls and which can be employed without the necessity ofincorporating therein an addition agent to impart good lubricatingqualities thereto.

I have discovered that the lubricity of synthetic lubricating oils canbe'materially enhanced by submitting such oils to an extremely mildsulfurization. By an extremely mild sulfurization I 50 meansulfurization of the synthetic lubricating oils to obtain a finalproduct containing only from about 0.0005% sulfur to about 0.5% sulfurand preferably about 0.005% to about 0.05%. I have discovered thatsynthetic lubricating oils suliurized to this extremely small extentevidence much improved lubricity and can be successfully employed in thelubrication of internal combustion engines.

The present invention is not to be confused with the prior practice of.sulfurizing lubricating 5 oils, or of adding a sulfurized material tolubricents to impart thereto extreme pressure properties. I am aware ofthis prior practice and make no claim to the sulfuriaation oflubricating oils or to the addition of sulfurized materials to syntheticlubricating oils to impart extreme pressure properties to suchlubricants. Although my synthetic lubricant possesses substantially noextreme pressure properties, it is nevertheless very eifective inproviding adequate lubrication for internal combustion engines. Bythe-term "possessing substantially no extreme pressure properties asapplied to my lubricant I mean a lubricant which willnot pass any of theaccepted methods of testing extreme pressure lubricants, such as theAlmen test, described by Wolf and Moughy in their paper on ExtremePressure Lubricants given at thel3th Annual Meeting of the A. P. I. atHouston, Texas, November 17, 1932.

My invention can be more clearly understood from the followingdescription thereof in which a synthetic lubricating oil obtained by thepolymerizatlon of isobutylene is employed by the way of example todescribe the same. The synthetic lubricating oil used in this example ismade by subjecting liquid isobutylene or a hydrocarbon mixturecontaining it to the action of boron fluoride at ordinary temperatures,for example, temperatures of about 0 F. to about 100 F. The resultantpolymerization product is carefully distilled to remove from it theexcessively light and heavy polymerization products which areunsatisfactory. More specifically, in the preparation of this syntheticlubricating oil, liquid isobutylene, or a hydrocarbon mixture containingthe 40 same, is maintained under pressure and cooled to 9. temperatureor about 32 F. and about 0.1% to about 2% of boron fluoride is addedwith vigorous agitation. Excessive rise in temperature due to the heatof reaction is avoided by suitable efficient cooling means. In order tofacilitate agitation in handling and to assist in controlling thereaction, I prefer to employ a diluent such ashexane, liquid butane,propane, naphtha, or the like. As an example of a hydrocarbon mixturecontaining isobutylene, I may employ the butanebutylene fractionrecovered from petroleum gases, especially those gases produced in thecracking of petroleum oils-for the production of gasoline. This lightfraction contains from about 10% to about 25% of isobutylene.

Afterthe isobutylene has been subjected to the action of the boronfluoride catalyst for about minutes, the catalyst is neutralized and thelight unreacted hydrocarbons removed by evaporation. The resultantreaction product is a viscous oil having the following characteristics:

Saybolt Universal viscosity at 100 F 1538 Saybolt Universal viscosity at210 F 117 Viscosity index of about 101 Flash about 250 F. Pour pointabout F.

This product may be further improved by subjecting the same to vacuumdistillation to obtain a material free of undesirable low boilingconstituents and undesirable high molecular weight constituents. I havediscovered that a fraction having the following characteristics is mostdesirable for the intended purpose.

Saybolt Universal viscosity at 210 F to 95 secs.

Viscosity index to Pour point -35 F.

The synthetic lubricating oil so obtained is subsequently heated at atemperature of about 375 F. to about 400 F. for about 60 to 120 minuteswith suflicient sulfur to give a resultant productcontaining not morethan about 0.05% sulfur. In place of using elemental sulfur, I may treatthe synthetic lubricating oil with sulfur chloride. However, wheneifecting the sulfurization with the latter, the reaction is carried outat a temperature of about to F. for about '30 minutes and finally at atemperature of about I claim is:

1. A lubricating oil possessing substantially no extreme pressureproperties adapted for use in internal combustion engines comprisingsubstantially a synthetic lubricating oil obtained by the condensationof an olefin and containing from about 0.0005% to about 0.05% stablybound sulfur.

2. A lubricating oil possessing substantially no extreme pressureproperties adapted for ,use in internal combustion engines comprisingsubstan-- of boron fluoride and containing from about 0.0005% to about0.05% stably bound sulfur.

3. As a new-composition of matter a synthetic lubricating oil possessingsubstantially no extreme pressure properties obtained by thecondensation of an isoolefin with boron fluoride at a temperature ofabout 0 F. to about 100F. and sulfurized to the extent of from about0.0005% to about 0.05% sulfur.

4. A synthetic lubricating oil possessing substantially no extremepressure properties adapted for the lubrication of internal combustionengines without causing scoring and scufling of the pistons and cylinderwalls of said engine comprising substantially a sulfurized syntheticlubricating oil obtained by the condensation of isobutylene with boronfluoride at a temperature of from about 0 F. to about 100 F., saidsulfurized synthetic lubricating oil containing a substantial amount butnot more than about 0.05% sulfur.

5. A method of preparing a synthetic lubricating oil possessingsubstantially no extreme pressure properties for use in internalcombustion engines and free of any tendency to cause scoring andscufling of the pistons and cylinder walls of said engine comprisingreacting an isoolefin with boron fluoride at a temperature of about 32F., neutralizing the unreacted boron fluoride, separating the resultantcondensation product and subsequently heating said condensation productat a temperature; between about 375 F. and about 400 F. for about 1 to 2hours in the presence of elemental sulfur to obtain a final productcontaining not more than about 0.05% sulfur.

6. The method of preparing a synthetic lubricating oil as described inclaim 5 in which the isoolefin is isobutylene.

7. The method of preparing a synthetic lu-' bricating oil as describedin claim 5 in which the condensation product is vacuum distilled priorto sulfurization to give a product having a Saybolt Universal viscosityat 210 F. of from about 55 seconds to about 95 seconds, a viscosityindex of from about 80 to about 95 and a pour point of about 25 F.

WILLIAM B. PLUMMER.

